4;

Adding unity to each side, in order to complete the

2

2

= + +15.

х

square;

1 841 232

.. 81 x2+18+

+16;

х

and extracting the root, 9x+ = ± (29 +4).

Ꮖ

;

16

But if the negative value be taken, 9x+4x=-30;

108

SECT. V.

Solution of Adfected Quadratics, involving two unknown Quantities.

(29.) If the equations involve two unknown quantities, they may, by the preceding rules, be reduced to one containing only one of the unknown quantities, the values of which may be found by Art. 28; whence, by substitution, the values of the other may also be determined. In many cases, however, it may be convenient to solve the equations first, considering one of the quantities as known`; when the rules for exterminating unknown quantities (23) may be more easily applied.

From the second equation, x=2y2;

Substituting this in the first, 2y-y= 15;